Do you mean E05 OL? E03 is an over-voltage condition (input voltage exceeds 15.5v). E05 is overload. There should be an alarm beeping along woith an E05 OL code too. But maybe that's just on the XM1800 model, which has more features as well as higher wattage.
XM1000 owner manual
Are you connected to shore power, i.e. the converter/charger is producing DC voltage instead of battery power alone?
2004 American Tradition; 2013 Buick Verano
Homebase in the Ocala Nat'l Forest near Ocala, FL